2.5 Blockade - July 1941 to April 1942

2.5.1 Avonmouth Smoke Screen

Although German bombers continued to carry out raids against Bristol during May, June and early July 1941, they were only relatively small scale affairs undertaken mainly by aircraft unable to locate their targets in the Midlands and North of England. Nevertheless, in the Autumn of 1940 the Ministry of Home Security decided that smoke screens should be provided to cover vital targets such as munitions factories, dams and ports and personnel of the Pioneer Corps had been selected to undertake the task. In October the first Smoke Companies were formed, but it was to be June 25th 1941 before No.810 (SM) Company arrived in the Bristol area to operate a screen around Avonmouth Docks. Two types of smoke generator were used, the old No.24 Mark II and the newly introduced Haslar. The Mark II, known as the 'smoke pot', was a small and entirely static piece of equipment fitted with tall chimneys and operated by hand. It used Pool Diesel Oil and had a burn time of 5 hours, hence the fact that they were arranged in pairs to cover up to 10 hours of operation. By contrast, the Haslar was mounted on a trailer and towed by a lorry, the complete installation being sent each night to the required location. Haslars produced biscuit coloured smoke by means of partly burnt oil enclosed in a film of water which was comparable in colour, nature and consistency to a London fog and were able to produce some 50 times the quantity of smoke generated by the Mark II's.

The Avonmouth Smoke Screen, which was first used early on the morning of July 5th, was made up of an Outer Circuit of up to 45 Haslars arranged on a radius of about 1500 yards around the target and an Inner Circuit formed by 2510 Mark II generators installed about 1000 yards out from the target, notably along the Portway, Portview Road and St.Andrew's Road, with the individual generators spaced in pairs at intervals of around 5 to 10 yards. This Inner, or 'quick cover', Circuit was lit instantaneously by exploders and provided a satisfactory screen during the interim period whilst the smoke from the Haslars joined up and covered the target. However, not all the generators were in use at any one time, as only that part of the screen lying within 60 degrees either side of the predicted wind would be utilised.

2.5.2 'Meacon' Radio Countermeasures

During their operations against Britain the Luftwaffe also made use of radio beacons located in France to assist aircraft navigation, and even against these radio countermeasures were employed. Instead of straightforward jamming, it was decided to receive and then re-radiate each individual beacon's signal from a transmitter located in Britain, thereby effectively falsifying the beacon's position. The transmitters involved were known as Masking Beacons or 'Meacons', the first having been installed in the region at Temple Combe in late August 1940, with an associated receiving station at Kington Magna. This was followed by a transmitting and receiving station opening at Highbridge in November, the transmitter from which was transferred to a separate site at Lympsham in March 1941.

The first success came some months later when, on the early morning of July 24th, the Lympshan transmitter, then re-radiating the Brest beacon, caused a Ju 88 of I/KG 30 which had been on a mission to Birkenhead Docks to land undamaged at RAF Broadfield Down, which at that time was still under construction. Low on fuel and thinking they were over France, the crew put down at 06.20 hrs, to make the first landing on what is now the main runway of Bristol's Lulsgate Airport, the Junkers subsequently entering service with the RAF as EE205!

2.5.3 Gun-Laying Radar Improved: August and September 1941

By late July the majority of Luftwaffe units previously engaged in operations over Britain had moved to the eastern front and were locked in combat over Russia, leaving only a few odd formations, mostly composed of anti-shipping aircraft, to continue the holding campaign against Britain. However, it was not realised at the time that the bombers would never again return to Bristol in force, so the defences were constantly improved during the next three years, one of the first upgrades made involving the replacement of the original gun-laying radar with superior sets which had a maximum range of 50,000 yards. During July and August this equipment was installed on the Portbury, Gordano, Pilning, Rodway, Keynsham and Whitchurch positions, and although it was a great improvement on the earlier versions difficulty was still experienced when following targets that took evasive action, a problem which was not solved until the introduction of microwave radar in 1943.

2.5.4 'Z' Rocket Sites Arrive: September 1941 to March 1942

During September the construction of the first rocket firing 'Z' sites in the Bristol area, under the 9th Anti-Aircraft 'Z' Regiment, had been completed at Easton in Gordano, which was positioned to cover Avonmouth Docks and at Bishopsworth for the defence of Bristol Docks. A further four sites were also planned, but only two of these, at Brislington and Abbots Leigh, were ever completed. The weapons themselves, known as 'Unrotated Projectiles' or UP's, being launched in salvoes of 128 to a maximum height of 19,000 feet, using 64 twin-projectors per site. The 'Z' batteries were well suited to firing barrages but the locations and discharge directions had to be carefully chosen to minimise the danger from falling tailpipes.

Although by the end of September Easton in Gordano was fully armed, and both sites equipped with gun laying radar sets, it was not until early March 1942 that the last ten Twin UP projectors arrived at Bishopsworth. Towards the end of the year it was also decided to mount 'Z' projectiles on certain 'Starfish' sites in sets of twelve, electrically coupled, so that they could be fired in salvoes of four to give realism and the illusion that the anti-aircraft barrage had been extended.

2.5.5 Searchlight Belts Introduced: Late 1941

In the late summer of 1941 the GCI stations in operation were only capable of directing one night fighter at a time, and as an interception took about ten minutes, the system could easily become saturated. To enable more aircraft to go into action against the massed raiding forces that were expected to return that winter, a new system to direct fighters to their target was introduced using the searchlights, many of which were now radar controlled. In September it was ordered that they were henceforth to be deployed as single lights arranged in 'Indicator Belts', using low powered projectors on a 10,500 yard spacing and in 'Killer Belts' with high powered projectors on a 6000 yard spacing, the necessary declustering being completed by late November. The 'Indicator Belts' along the South Coast pointed out the incoming raiders before they entered the 'Killer Belt' where, to protect the Bristol area, the Colerne Sector had five RAF fighters orbiting vertical searchlight beams which acted as beacons, these lights depressing and pointing the interceptors towards their assigned targets as the enemy bombers approached. Code named 'Smack', this procedure was to operate in parallel with the GCI system for the remainder of the war and was of great help to the night fighters.

2.5.6 Women & Home Guard to the Gun and Balloon Sites: September 1941 to June 1942

Throughout the war Anti-Aircraft Command tended to be treated as a reserve for the Army in general, with men constantly being transferred to other formations and theatres of operation, a good example of this being the local 76th Heavy Anti-Aircraft Regiment which started its move from the Bristol area to North Africa in November 1941. In an attempt to maintain manning levels it was therefore decided to recruit women from the Auxiliary Territorial Service to form 'mixed' batteries made up of both men as well as women, who would carry out nearly all the duties done by the men except actually firing the guns. As a first step towards this on September 22nd the 133rd (M) Heavy Anti-Aircraft Regiment had been formed at Clifton, and shortly after women were assigned for service on some twelve heavy anti-aircraft sites around Bristol.

The use of women was also extended to the 'Z' batteries, while female crews from the Women's Auxiliary Air Force took over the responsibility for a number of barrage balloon sites around the city, but not before the somewhat crude living conditions often associated with these had been improved. Nevertheless, the WAAF's still had to endure the weather as well as the danger of attack from the air, and although theirs was one of the hardest jobs undertaken by women during the war, they carried out the complicated balloon operations with all the ease and efficiency of men.

Searchlights, however, posed more problems and it was soon realised that it was totally impractical to employ 'mixed' manning on the remote and spartan searchlight sites which existed in most parts of the country. Consequently the 68th Searchlight Regiment, responsible for the projectors deployed in the Bristol area since November 1941, remained a 'men only' unit for the rest of the war.

Although ATS manning had done much to keep the anti-aircraft units up to strength, even this source was starting to dry up. Attention therefore turned elsewhere and in late February 1942 the first Home Guard volunteers commenced manning Bristol's heavy anti-aircraft guns, while at the end of June they also started to take over responsibility for a local 'Z' sites.

2.5.7 Lulsgate Airfield Opened: January 1942

In early January 1942 the last planned fighter airfield in the area was also being completed, and although originally christened RAF Broadfield Down, the name was changed to Lulsgate Bottom before it officially opened in mid-January. By this time, however, the air war was receding from the West Country, and with Colerne and Charmy Down providing adequate cover for the area, another local fighter airfield was unnecessary. No operational units were therefore based there, and in June the aerodrome was taken over for flying training purposes.

2.5.8 Charmy Down and the 'Turbinlite' Experiment

The beginning of 1942 also saw the start of a bizarre experiment involving the Hurricanes of No.87 Squadron working in cooperation with radar equipped Havocs and Bostons of No.1454 Flight which carried an airborne searchlight in the nose. It was hoped that the Havocs would be able to illuminate the target with a powerful light, known as 'Turbinlite', while a Hurricane flying in formation shot down the enemy bomber. Although this idea was fraught with difficulties the first patrol by a Havoc and Hurricane combination was flown in late March, but despite increased operations in the summer the Havocs and Bostons at Charmy Down were only able to make four unsuccessful contacts. Nevertheless, it was to be January 1943 before the last 'Turbinlite' left Charmy Down, after which it ceased to be a fighter airfield involved in local defence, the Hurricanes of No.87 Squadron having been transferred to North Africa in November 1942